SEA-FISHERIES LABORATORY. 233 



The cells of tlie coelomic epithelium and the coelomic 

 corpuscles perform excretory functions ; carmine granules 

 injected into the coelom are taken up by these cells and by 

 •the nephridia (see Gr. Schneider, Zeitschrift fur Wiss. 

 Zoologie, Band 66, pp. 505-507, 1899). Chlorogogen 

 granules are present in many of the cells of the coelomic 

 epithelium. 



A great proportion of the reproductive cells present 

 in the coelomic fluid, instead of floating freely, accumulates 

 in the space between the oblique muscles and the ventral 

 body wall. In females oocytes in various stages of growth 

 and varying in diameter from 02 — '16 mm. may be seen. 

 In males various stages in the development of spermatozoa 

 from groups of young spermatogonia, consisting of about 

 eight cells to the masses of spermatids seen in Fig. 65, 

 may be found. 



The coelomic fluid is kept in motion hj contractions 

 of the body wall. In a specimen freshly taken from the 

 sand one usually observes a series of peristaltic waves 

 arising in the posterior part of the gill region, and 

 running forwards to the anterior end, producing a pro- 

 gressive swelling of the body, due to the carrying forward 

 of the coelomic fluid, which, as soon as the wave is past, 

 flows backwards again. This motion is of considerable 

 importance in promoting the efficient circulation of the 

 coelomic fluid, in inflating the anterior portion of the 

 animal, thus aiding in burrowing, in assisting the com- 

 paratively weak gut muscles to cause the backward motion 

 of the sand in the alimentary canal, and, when the animal 

 is in its burrow, in providing frequent changes, practically 

 a current, of sea-water to bathe the external surface and 

 the gills. 



